In radio telecommunications systems of today a number of different types of base stations are provided serving different sizes of coverage areas. Some base stations serve bigger coverage areas, called macro cells, and some serve smaller areas, called micro cells. Today solutions of small radio cells with access control, so called femto solutions or home base stations are provided to serve small cells, for example, home base stations are provided in Wideband Code Division Multiple Access/Universal Terrestrial Radio Access Network (WCDMA/UTRAN) and in Evolved Universal Terrestrial Radio Access Network (E-UTRAN) also called the Long Term Evolution (LTE) Radio Access Network (RAN). The core network, to which E-UTRAN is connected, is called Evolved Packet Core (EPC), a.k.a. System Architecture Evolution (SAE) network. Both the E-UTRAN and the EPC comprise together the Evolved Packet System (EPS) that is also known as the SAE/LTE network. A base station of EPS is called E-UTRAN NodeB (eNodeB or eNB). An E-UTRAN base station provided for a home or small area coverage for a limited number of users is herein called Home eNodeB (HeNB). For WCDMA/UTRAN, this type of a home access point is called Home NodeB (HNB).
The HeNB provides radio coverage for the end users and is connected to a mobile core network using some kind of Internet Protocol (IP) based transmission. The radio coverage provided by the HeNB is herein called femtocell.
This way of providing Local Access enables cheaper call or transaction rates/charges when connected via an HeNB compared to when connected via an eNB. It may also reduce the load on an operator's eNBs and backhaul connections and thereby reduce the operator's Capital Expenditures (CAPEX) and Operating Expenditures (OPEX).
An HeNB uses, in most cases, an already existing broadband connection, e.g. Digital Subscriber Line (xDSL), Cable or the like, of the end users to achieve connectivity to the operator's mobile core network and possibly to other eNB/HeNB. Over the broadband connection and via other possible intermediate IP networks, e.g. in the internet, an HeNB communicates with the core network nodes in the operator's network using an Internet Protocol Security (IPsec) tunnel, defined in Internet Protocol security architecture according to RFC 4301. The IPsec tunnel is established between the HeNB and a Security Gateway (SEGW), wherein the SEGW protects the border of the operator's network.
An exemplary LTE/SAE network comprises both femto and macrocells, wherein a user equipment (UE) is arranged to be connected to a core network (CN). A number of HeNBs is arranged in the network to serve a respective femotcell through which the UE may be connected to the CN. The exemplary LTE/SAE network may further comprise a HeNB Gateway (HeNB GW). The main reasons for having a HeNB GW between the HeNBs and the CN are the following:                the assumed number of HeNBs in a network is very high, for example, millions of HeNBs is one estimate. This will possibly create a scaling problem in the CN side as each HeNB will have its own S1 interface and it is assumed that Mobility Management Entities (MMEs) of the CN are not capable of handling millions of S1 interfaces;        end users may switch on and off the HeNBs frequently causing increased signaling load between the HeNB and MME over the S1 interface. This will possibly create a signaling load problem in the CN side and mostly in the MME due to HeNB S1 interfaces being frequently disconnected and reconnected; and        HeNBs may be tampered with e.g. malicious/modified software. This will possibly create a security problem in both the MME and Serving Gateway (S-GW) as any HeNB that is able to establish an IPsec tunnel to a security gateway of the operator's network may attack these nodes.        
The HeNB GW 30 solves these scaling, signaling load and security problems.
Furthermore, the radio telecommunications system further comprises a number of eNBs each serving a macro cell. The macro cells are overlaying the femto cells. The UE may also use the macro cells to connect to the CN over S1 interfaces.
In the SAE/LTE and WCDMA/UTRAN 3GPP standards a concept known as Closed Subscriber Group (CSG) has been introduced. With CSG, particular HeNBs, may be associated to certain UEs, meaning that only these associated UEs are allowed to access the HeNBs. The allowed CSG Identities (CSG-ID) for a particular UE are stored in the UE in a so called Allowed CSG List. Thus, the Allowed CSG List comprises the CSG-IDs of the CSGs of which the subscriber is a member and may also comprise any additional qualifying or quantifying data associated with each CSG membership. An example of additional data is the CSG Type, which is a piece of textual or graphical information that the operator specifies and may associate with a CSG-ID in an Allowed CSG List. The purpose of the CSG Type is to display useful information on the UE, e.g. to give the user a hint on the applicable charging rates, such as “home”, “visited” or “campus”. Different users may have different CSG Type data associated with the same CSG-ID.
Each HeNB broadcasts in System Information (SI) both a CSG Indicator, a Boolean type of indicator, and the CSG-ID allocated to it. This means that the UE may determine by reading the CSG-ID from the SI and comparing this to the contents of the Allowed CSG List whether it is allowed to access a particular HeNB or more correctly the femtocell i.e. a CSG cell, associated with the SI and served by the HeNB as a HeNB could theoretically serve multiple femtocells and each of these cells may, at least theoretically, belong to different CSGs.
The Allowed CSG List for the UE is also stored in the CN, so that the CN may perform an ultimate access control, e.g. in case a hacked UE is used that has an outdated Allowed CSG List or misbehaves. Then the CN will have the latest Allowed CSG List of the UE and will know which CSG the UE is allowed to access. The administration related to the handling of which UEs are allowed to access a specific HeNB, or which UEs that should be added to the CSG of a HeNB, is performed by a CSG Manager.
Another concept related to the Allowed CSG List and femtocells is called radio cell footprint, may also be called radio cell fingerprint. This information defines the location of a specific CSG femtocell in relation to, for example, the overlaying macrocells, microcells, picocells and other femtocells. Thereby, the occasions when the UE needs to unnecessarily search for the allowed CSG femtocells is minimized as the UE may only search for a specific CSG femtocell when there is a match with the radio cell footprint associated with the CSG femtocell. Consequently also the negative impact this unnecessary search would have on the UE battery lifetime is minimized.
One possible variant to distribute the CSG information to the UEs could be enhancement of Non Access Stratum (NAS) signaling between the CN, that is, the MME or MSC/SGSN, and the UE. Another possibility could be usage of Short Message Service Over-The-Air (SMS OTA) configuration of the UE. The enhancement of NAS signaling means that all the MMEs, MSCs and/or SGSN nodes would need to be updated to support a distribution functionality. SMS OTA is a proprietary solution.
The assumed HeNB Operation and Maintenance (O&M), that is, the automatic configuration of the HeNBs, based on an Automatic Configuration Server (ACS), described below, is not appropriate for O&M of the UEs, i.e. downloading of the CSG related information to the UEs. For example, it does not fit well for the downloading of the Allowed CSG List information to the UEs as there are no mechanisms for the UEs to communicate with the ACS. This creates the problem that it is not possible to combine the O&M of the HeNBs with the limited O&M of the UEs in the same logical entities and therefore not gain from the possibility to coordinate information between these different O&M variants. There is a desire to distribute CSG information and CSG related information of any types of radio cells where the CSG concept is applied to in an efficient manner.